package com.study.sqlSession;

import com.study.config.BoundSql;
import com.study.pojo.Configuration;
import com.study.pojo.MappedStatement;
import com.study.utils.GenericTokenParser;
import com.study.utils.ParameterMapping;
import com.study.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        PreparedStatement preparedStatement = getPreparedStatement(configuration, mappedStatement, params[0]);

        // 5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();

        // 6. 封装返回结果集
        // 获取结果集的全路径
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();
        while (resultSet.next()) {
            Object resultObject = resultTypeClass.newInstance();

            // 元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i < metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段值
                Object value = resultSet.getObject(columnName);

                // 使用反射，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = null;
                try {
                    propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                } catch (Exception ignored) {

                }
                if (propertyDescriptor == null) {
                    continue;
                }
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(resultObject, value);
            }
            objects.add(resultObject);
        }
        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        PreparedStatement preparedStatement = getPreparedStatement(configuration, mappedStatement, params[0]);

        // 5. 执行sql
        int resultSet = preparedStatement.executeUpdate();
        return resultSet;
    }

    /**
     * 设置参数
     *
     * @param configuration
     * @param mappedStatement
     * @param param
     * @return
     * @throws SQLException
     * @throws ClassNotFoundException
     * @throws NoSuchFieldException
     * @throws IllegalAccessException
     */
    private PreparedStatement getPreparedStatement(Configuration configuration, MappedStatement mappedStatement, Object param) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        // 1. 注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql语句
        // 转换sql语句，变量#{id}变成？，转换的过程中，还需要对#{}的值进行解析存储
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3. 获取预处理对：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        // 4. 设置参数

        // 获取参数的全路径
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            // 反射
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            // 暴力访问，设置成可访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(param);
            preparedStatement.setObject(i + 1, o);
        }
        return preparedStatement;
    }

    /**
     * 获取目标类
     *
     * @param parameterType
     * @return
     * @throws ClassNotFoundException
     */
    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 对#{}做解析，使用？进行代替
     * 解析出#{}的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        // 标记处理类：配置标记解析器完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        // 解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        // 解析出来的参数名
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }
}
